This circuit, from the 70's, can be assembled with a more modern FET like the BF245. The circuit is powered by a 9 V battery, as its consumption is very low.
This circuit allows the detection of RF signals using the lowest range of direct currents of a...
This circuit is from a National Semiconductor manual, appearing elsewhere on this site. The...
The transformer inf this circuit is a 6 or 9 V unit and diodes 1N4002. The filter capacitor is 2...